As mobile station users travel with their devices (e.g. mobile phones, mobile computers, and mobile broadband modems), a number of processes must take place to assure continuous service. One of the processes is an idle redirection between channels (i.e. frequencies). Channel redirection is used to increase the mobile network's performance by distributing the use of bandwidth over different frequencies. Channel redirection is also needed to try to avoid co-channel interference among nearby base stations or antennas.
The current frequency selection methodology sends a message from a base station over that particular sector's channel that tells all mobile stations on that particular channel to retune to a different specific channel. Any mobile station that receives the message is redirected. There are many disadvantages to the current scheme. One is that the area that needs to be redirected is only roughly controlled by radio frequency (“RF”). Not all mobile stations within the sector need the redirection signal.
Additionally, on border areas, only mobiles in part of a coverage area need to be redirected to the new channel. The mobile stations that do not need to be redirected are taking up bandwidth on the new channel and are leaving a channel that could be partly used. This underutilizes some sector-channels and over-utilizes others and can impact the wireless capacity of the area serviced by that sector.
As noted above, a further difficulty with the existing redirection procedure is that mobile stations that need to acquire the signal to be redirected, may not receive the signal. Alternately, redirect signals from within the network leak into a border area that does not require redirection and those mobile stations are now set for redirection. Both of these scenarios also lead to a reduction in capacity on those sectors. Further, mobile stations that travel into an intended redirection area can miss the redirection message if the mobile station is idling on a sector-channel that is not transmitting the redirection message. This leads to the occurrence of dropped calls or failed call attempts.
Sector areas are limited by the channel (frequency) transmitted over RF. The sectors, at their most basic, are subdivisions of the transmission area of the base station antenna. FIG. 1A illustrates a base station 19 in the center of three sectors 5 transmitting redirect signals 7. So while a sector may be geographically determined it actually controlled by RF and RF is inherently difficult to control.
Hence, a need exists for a system that will allow mobile stations to properly place themselves on the proper frequency (channel) without the need to acquire or communicate with a mobile network system.